Sound reproduction systems in which decoding or matrixing is carried out by the manner in which the loudspeakers are connected to the outputs of power amplifiers are disclosed in Gerzon "Surround Sound from 2-Channel Stereo", Hi-Fi News, August 1970, page 1104 and Hafler, "2-Channel Quadraphony", Hi-Fi News, August 1970, page 1111. However, in these previous proposals, there exists at least one set of three loudspeakers for which there is a non-zero linear combination of their voltages. In other words the signals fed to such a set of three loudspeakers are not linearly independent and it has been found that such linear independence is desirable if authentic directional reproduction is to be achieved.